Photomasks are high precision plates containing microscopic images of electronic circuits. Photomasks are typically made from very flat pieces of quartz or glass with a layer of chrome on one side. Etched in the chrome is a portion of an electronic circuit design. This circuit design on the mask is also called “geometry.”
A typical photomask used in the production of semiconductor devices is formed from a “blank” or “undeveloped” photomask. As shown in FIG. 1, a typical blank photomask 10 is comprised of three or four layers. The first layer 11 is a layer of quartz or other substantially transparent material, commonly referred to as the substrate. The next layer is typically a layer of opaque material 12, such as Cr, which often includes a third layer of antireflective material 13, such as CrO. The antireflective layer may or may not be included in any given photomask. The top layer is typically a layer of photosensitive resist material 14. Other types of photomasks are also known and used including, but not limited to, phase shift masks, embedded attenuated phase shift masks (“EAPSM”) and alternating aperture phase shift masks (“AAPSM”).
The process of manufacturing a photomask involves many steps and can be time consuming. In this regard, to manufacturer a photomask, the desired pattern of opaque material 12 to be created on the photomask 10 is typically defined by an electronic data file loaded into an exposure system which typically scans an electron beam (E-beam) or laser beam in a raster or vector fashion across the blank photomask. One such example of a raster scan exposure system is described in U.S. Pat. No. 3,900,737 to Collier. Each unique exposure system has its own software and format for processing data to instruct the equipment in exposing the blank photomask. As the E-beam or laser beam is scanned across the blank photomask 10, the exposure system directs the E-beam or laser beam at addressable locations on the photomask as defined by the electronic data file. The areas of the photosensitive resist material that are exposed to the E-beam or laser beam become soluble while the unexposed portions remain insoluble. In order to determine where the E-beam or laser beam should expose the photoresist 14 on the blank photomask 10, and where it should not, appropriate instructions in the form of a jobdeck need to be provided to the processing equipment.
After the exposure system has scanned the desired image onto the photosensitive resist material 14, as shown in FIG. 2, the soluble photosensitive resist material is removed by means well known in the art, and the unexposed, insoluble photosensitive resist material 14′ remains adhered to the opaque material 13 and 12. Thus, the pattern to be formed on the photomask 10 is formed by the remaining photosensitive resist material 14′.
The pattern is then transferred from the remaining photoresist material 14′ to the photomask 10 via known etch processes to remove the antireflective material 13 and opaque materials 12 in regions which are not covered by the remaining photoresist 14′. There is a wide variety of etching processes known in the art, including dry etching as well as wet etching, and thus a wide variety of equipment is used to perform such etching. After etching is complete, the remaining photoresist material 14′ is stripped or removed and the photomask is completed, as shown in FIG. 3. In the completed photomask, the pattern as previously reflected by the remaining antireflective material 13′ and opaque materials 12′ are located in regions where the remaining photoresist 14′ remain after the soluble materials were removed in prior steps.
In order to determine if there are any unacceptable defects in a particular photomask, it is necessary to inspect the photomasks. A defect is any flaw affecting the geometry. This includes undesirable chrome areas (chrome spots, chrome extensions, chrome bridging between geometry) or unwanted clear areas (pin holes, clear extensions, clear breaks). A defect can cause the customer's circuit not to function. The customer will indicate in its defect specification the size of defects that will affect their process. All defects of that size and larger must be repaired, or if they cannot be repaired, the mask must be rejected and rewritten.
Typically, automated mask inspection systems, such as those manufactured by KLA-Tencor or Applied Materials, are used to detect defects. Such automated systems direct an illumination beam at the photomask and detect the intensity of the portion of the light beam transmitted through and reflected back from the photomask. The detected light intensity is then compared with expected light intensity, and any deviation is noted as a defect. The details of one system can be found in U.S. Pat. No. 5,563,702 assigned to KLA-Tencor.
After passing inspection, a completed photomask is cleaned of contaminants. Next, a pellicle may be applied to the completed photomask to protect its critical pattern region from airborne contamination. Subsequent through pellicle defect inspection may be performed. In some instances, the photomask may be cut either before or after a pellicle is applied.
To perform each of the manufacturing steps described above, a semiconductor manufacturer (e.g., customer) must first provide a photomask manufacturer with different types of data relating to the photomask to be manufactured. In this regard, a customer typically provides a photomask order which includes various types of information and data which are needed to manufacture and process the photomask, including, for example, data relating to the design of the photomask, materials to be used, delivery dates, billing information and other information needed to process the order and manufacture the photomask.
A long standing problem in the manufacture of photomasks is the amount of time it takes to manufacture a photomask from the time a photomask order is received from a customer. In this regard, the overall time it takes to process a photomask order and manufacture a photomask can be lengthy, and thus, the overall output of photomasks is not maximized. Part of this problem is attributable to the fact that many customers who order photomasks often place their orders in a variety of different formats which are often not compatible with the photomask manufacturer's computer system and/or manufacturing equipment. Accordingly, the photomask manufacturer is often required to reformat the order data and condition, convert, and/or supplement it to a different format which is compatible with its computer system and/or manufacturing equipment, which can take a great deal of time, and thus, delay the time it takes to manufacture a photomask.
In an attempt to address these problems, the photomask industry has developed various standard photomask order formats in which photomask orders should be placed. For example, the SEMI P-10 standard is one standard format used in the manufacture of photomasks. Additionally, a few semiconductor manufacturers have developed their own proprietary photomask order format in which photomask orders are to be placed, rather than adopting a standard format. These standard and proprietary photomask order formats were created so that photomask orders would be received from customers in a uniform format, thereby reducing the overall time it takes to manufacture a photomask.
Although the use of such standard and/or proprietary photomask order formats are useful in reducing the time it takes to manufacture photomasks, many semiconductor manufacturers have been reluctant to place their photomask orders in such standard and/or proprietary formats for a variety of reasons. For example, the SEMI P-10 standard order format is quite complicated and requires the customer placing the order to have a sophisticated working knowledge of the requirements associated with such standard. Since many semiconductor manufacturers do not manufacture photomask, such manufacturers may not have the resources, time or ability to learn the intricacies of such standard format. Thus, semiconductor manufacturers often provide a photomask manufacturer with photomask order data in an unorganized and often incomplete manner. As a result, the photomask manufacturer is required to parse through this data and organize it in a useful format (e.g., in the SEMI P-10 format). Additionally, in those instances where incomplete photomask order data is provided to a photomask manufacturer, such manufacturer will be required to request the missing information from the customer. As a result, a great deal of time is often wasted in the process of obtaining a complete and accurate photomask order, and thus, the overall time that it takes to manufacturer a photomask can be greatly delayed. There has been a long felt need in the field of photomask manufacture for a customer side system and method for automatically generating a complete and accurate photomask order in a standard and/or proprietary format.
In the past, AlignRite Corporation (a predecessor organization to Photronics, Inc.), attempted to expedite the delivery of the electronic data through the use of an Internet based delivery system. However, although the AlignRite System was capable of rapid delivery of the photomask data from a customer to the computer system of the photomask manufacturer and was capable of validating the accuracy of this data in real time, this prior system did not provide for the automated generation of photomask order data in a single standard and/or proprietary format. In this regard, once the data was received from the customer, standard modifications to the data would also have to be entered manually by operators. Each time a manual change would have to be entered, the risk of human error increased and the overall length of the job would be extended.
Others have disclosed systems in which manufacturing and billing data are down-loaded over the Internet and verified on-line automatically. One such system is described in PCT Publication Number 02/03141, published on Jan. 10, 2002 to DuPont Photomask, Inc. More particularly, the DuPont Publication discloses a system in which photomask order data is entered on-line by a customer and transmitted to a photomask manufacturer for processing. In this system, a customer is prompted to enter photomask order data. Such data is transmitted to a photomask manufacturer, who in turn performs a diagnostic evaluation of the data. If any data is incomplete or inaccurate, the system sends a message to the customer notifying him of such error. Thereafter, the user must correct the error. After the data has been validated by the manufacturer (and corrected when necessary), the manufacturer processes this data and puts it into a standard (or proprietary) format, such as the SEMI P-10 standard format.
Although useful for diagnostic purposes, the system of the DuPont PCT Publication is very cumbersome and provides a user with very little flexibility in formulating a photomask order or in using information previously entered in prior orders. Further, the system of the DuPont PCT Publication also requires a user to interact through a predefined graphical user interface (“GUI”) which is particularly cumbersome and limiting on the user. Thus, there is a long felt need for a system and method which generates photomask orders that are simple and flexible, and avoid the necessity of reentering the data previously used in prior photomask orders.
After the manufacturing steps described above are completed, the completed photomask is sent to a customer for use to manufacture semiconductor and other products. In particular, photomasks are commonly used in the semiconductor industry to transfer micro-scale images defining a semiconductor circuit onto a silicon or gallium arsenide substrate or wafer. The process for transferring an image from a photomask to a silicon substrate or wafer is commonly referred to as lithography or microlithography. Typically, as shown in FIG. 4, the semiconductor manufacturing process comprises the steps of deposition, photolithography, and etching. During deposition, a layer of either electrically insulating or electrically conductive material (like a metal, polysilicon or oxide) is deposited on the surface of a silicon wafer. This material is then coated with a photosensitive resist. The photomask is then used much the same way a photographic negative is used to make a photograph. Photolithography involves projecting the image on the photomask onto the wafer. If the image on the photomask is projected several times side by side onto the wafer, this is known as stepping and the photomask is called a reticle.
As shown in FIG. 5, to create an image 21 on a semiconductor wafer 20, a photomask 10 is interposed between the semiconductor wafer 20, which includes a layer of photosensitive material, and an optical system 22. Energy generated by an energy source 23, commonly referred to as a Stepper, is inhibited from passing through the areas of the photomask 10 where the opaque material is present. Energy from the Stepper 23 passes through the transparent portions of the quartz substrate 11 not covered by the opaque material 12 and the antireflective material 13. The optical system 22 projects a scaled image 24 of the pattern of the opaque material 12 and 13 onto the semiconductor wafer 20 and causes a reaction in the photosensitive material on the semiconductor wafer. The solubility of the photosensitive material is changed in areas exposed to the energy. In the case of a positive photolithographic process, the exposed photosensitive material becomes soluble and can be removed. In the case of a negative photolithographic process, the exposed photosensitive material becomes insoluble and unexposed soluble photosensitive material is removed.
After the soluble photosensitive material is removed, the image or pattern formed in the insoluble photosensitive material is transferred to the substrate by a process well known in the art which is commonly referred to as etching. Once the pattern is etched onto the substrate material, the remaining resist is removed resulting in a finished product. A new layer of material and resist is then deposited on the wafer and the image on the next photomask is projected onto it. Again the wafer is developed and etched. This process is repeated until the circuit is complete. Because, in a typical semiconductor device many layers may be deposited, many different photomasks may be necessary for the manufacture of even a single semiconductor device. Indeed, if more than one piece of equipment is used by a semiconductor manufacturer to manufacturer a semiconductor device, it is possible more than one photomask may be needed, even for each layer. Furthermore, because different types of equipment may also be used to expose the photoresist in the different production lines, even the multiple identical photomask patterns may require additional variations in sizing, orientation, scaling and other attributes to account for differences in the semiconductor manufacturing equipment. Similar adjustments may also be necessary to account for differences in the photomask manufacturer's lithography equipment. These differences need to be accounted for in the photomask manufacturing process.
While the prior art is of interest, the known methods and apparatus of the prior art present several limitations which the present invention seeks to overcome.
In particular, it is an object of the present invention to provide a rule-based system and method for automatically generating a photomask order which is user friendly and avoids the necessity of re-entering data previously entered in the same or another order.
It is another object of the present invention to provide a rule-based system and method for automatically generating a photomask order which does not require the user to interact through a predefined graphical user interface.
It is another object of the present invention to provide a rule-based photomask order system and method for reducing photomask order and data entry times.
It is another object of the present invention to provide a rule-based photomask order system and method for reducing transcription errors associated with the manual entry of photomask orders.
It is another object of the present invention to provide a rule-based photomask order system and method for increasing the overall output of photomasks being manufactured.
It is another object of the present invention to solve the shortcomings of the prior art.
Other objects will become apparent from the foregoing description.